Cyclone frequency may rise over Indian coast from the warming of Pacific: study

Source: The post is based on the article “Cyclone frequency may rise over Indian coast from the warming of Pacific: study”  published in The Hindu on 30th August 2023

What is the News?

According to a study, the intensity and frequency of tropical cyclones are expected to increase in the north Indian Ocean.

What does the study say about the Tropical Cyclones?

Tropical cyclones do not form easily near the equator. The number of equatorial-origin cyclones was 43% less in the period from 1981 to 2010 compared with 1951 to 1980.

This happened because Pacific Decadal Oscillation(PDO) was in a ‘warmer’ or positive phase. 

However, in 2019, the PDO entered a cooler, negative phase. This could mean more tropical cyclones in the post-monsoon months that originate near the equator. 

This means more cyclones will be forming closer to India’s Peninsular coast for the North Indian Ocean region.

What is Pacific Decadal Oscillation(PDO)?

The Pacific Decadal Oscillation (PDO) is a long-term climate pattern that affects the temperature of the Pacific Ocean and the weather patterns around it. 

The PDO is a naturally occurring phenomenon that shifts between warm and cool phases, with each phase lasting around 20-30 years. 

The PDO has positive and negative phases.El Nino Southern Oscillation (ENSO) with a positive PDO is generally not good for India but when linked with a negative PDO, it brings more rain to India.

What is the difference between PDO and El Nino Southern Oscillation (ENSO)?

Firstly, the most obvious difference between the PDO and ENSO is the time scale.The El Nino Southern Oscillation (ENSO) phenomenon repeats in the Pacific over two to seven years.But the Pacific Decadal Oscillation (PDO) has a longer cycle as it repeats every 20 to 30 years.

Secondly, El Nino, often corresponds to reduced rainfall over India whereas La Nina, is linked to excessive rainfall over India.

– But unlike an ENSO whose stage can be determined any year, a ‘positive’ or ‘warmer phase’ of a PDO can be known only after several years of measuring ocean temperatures and their interaction with the atmosphere.